This invention relates to the field of finishing tools. It relates more particularly to an improved hub for a finishing disk.
A finishing member such as a finishing disk is normally removably attached by way of a hub assembly including a disk support pad to a power tool. When the hub is rotated, the disk rotates with it, permitting the moving disk surface to effectively finish the surface of work pieces such as furniture and automobile body parts. A variety of hub structures have been used heretofore to secure the finishing disk to the power tool. Perhaps the most common of these includes a support pad having a reinforced central aperture arranged to be engaged over the threaded end of the rotary shaft of the power tool. The finishing disk is placed on the flat surface of the pad and a flanged nut is turned down onto the shaft end protruding through the disk. When the nut is tightened, it lays flush against the abrasive surface of the disk and clamps the disk to the support pad.
That mode of attaching the finishing disk to the tool is disadvantaged in that engagement of the rotating finishing disk against a work piece imparts torque to the hub which tends to tighten the nut onto the threaded shaft of the power tool, making it quite difficult to remove the nut in order to replace the disk after it becomes worn. In many heavy industrial applications, the disks have to be replaced quite often, e.g. over five times per hour. Consequently, considering the number of tools in use on a given shift, there is an excessive amount of downtime necessitated by such disk replacement.
In order to avoid that problem, there has been developed a so-called quick release or snap-on finishing disk hub, two versions of which are described in U.S. Pat. Nos. 3,667,169 and 3,667,170. In those arrangements, an adapter is screwed onto the threaded end of the power tool shaft. The adapter may either be incorporated into a special disk support pad or may be in the form of a nut which is turned down onto the power tool shaft after placement on the shaft of a standard support pad. The remainder of the hub assembly consists of a flat annular plate having a centrally located, raised hollow boss.
In one version, the plate is adhered to the back of the finishing disk. In another version, the plate engages the front of the disk and has prongs which project through the disk and are bent against the rear face of the disk to secure the disk to the plate. In both types of plates, the raised boss has a central aperture whose rim is turned inward and shaped to form a screw thread. The boss projecting from the rear face of the article functions as a female component in receiving the threaded end of a stud on the adapter or the end of the power tool shaft itself. The plate and disk are rotated so that the stud or shaft is threaded into the boss until the boss bottoms in a socket formed in the adapter. As such, the boss functions as a male component bearing against the end of the socket. Simultaneously, the annular plate is supposed to engage the end of the adapter forming a two-point contact between the plate and the adapter to create an effective connection between the plate and the adapter.
In practice, however, that simultaneous contact is difficult to achieve unless relatively close tolerances are maintained for the hub parts which makes the hub relatively expensive to manufacture. Also, those prior hub assemblies, including the various spacers and washers required to adapt them to the difficult length threaded power tool shafts, comprise several separate parts which are easily lost. In addition, in the latter two prior hubs, the attachments of the plates to the power tool adapters have not been as strong as they might be.